1. Field of Invention
This invention relates to a method of molding parts, particularly molding resin infused fiberglass parts. This invention also relates to the components used for such molding, including the injector head and mold device.
2. Description of Related Art
Fiberglass parts infused with resin are commonly used as building components that require strength and durability at a low weight and cost. Such components are used in many vehicles, especially in the marine industry where such parts are valued for their superior waterproof and weather resistant properties.
Typically, fiberglass parts are made in open molds by laying down fiberglass sheet material, spraying resin onto the mold to saturate the fiberglass material and allowing the part to cure. During the molding process, if all of the fiberglass chopped strand is not coated with the resin or if it is applied in uneven thickness, the part may have uneven strength characteristics. Also, peeling, flaking and deterioration can result from incomplete or inconsistent lay-up. Thus, the even and consistent application of resin to the part is very important during the molding process.
Due to the current trend toward stricter environmental regulations, open molding is becoming disfavored. When using an open mold, the resin emits restricted compounds and noxious fumes, including styrene and curatives therefor, while curing. Presently, U.S. government regulations restrict the emission of styrene and its curatives, and overseas such emissions are often prohibited. To limit the environmental exposure and conform to regulations, methods of closed molding have been developed.
In one known method of forming a part in a closed mold, resin is infused into fiberglass by (1) covering the mold, (2) applying a vacuum at the center of the mold, and (3) applying resin near the edges of the mold and drawing the resin through the fiberglass toward the vacuum application point, using various films and flow enhancing techniques. Such vacuum assisted processes are generally known as VARTM (vacuum assisted resin transfer molding.) However, it is difficult to ensure complete and even infusion in such a method. Also, resin tends to be left in the supply channels and pulled into the vacuum source, which requires additional cleanup that increases costs and can create additional emission of fumes. The films and flow enhancing media are typically single use, incurring additional cost as well.
Thus, there is a need to provide a reliable method of infusion that results in consistently uniform infused parts while limiting the emission of restricted compounds.